(1) Field of the Invention
The present invention relates to the field of piloting an aircraft such as an airplane or a rotorcraft by means of at least two flight control members.
(2) Description of Related Art
Thus, below in the present application, the term “control member” is used to cover any control device suitable for being moved by a pilot or automatically, whether in a cockpit or outside the aircraft when the aircraft has a pilot who is not on board. Such control members may thus be in various forms and in particular they may be in the form of a lever, a stick, a joystick, or indeed in the form of pedals.
These control members then enable aerodynamic means to be moved relative to an incident air stream on a fuselage of the aircraft. In an airplane, such as aerodynamic means may then be constituted either by flaps, ailerons, or wind spoilers, or indeed a rudder or an elevator.
For a rotorcraft, such aerodynamic means may correspond to a collective pitch angle or to a cyclic pitch angle of the blades of a main rotor, or to a collective pitch angle of the blades, in particular of a tail rotor, for example.
More particularly, the invention relates to a method of controlling aerodynamic means of an aircraft, to an associated control system, and to an aircraft provided with the control system.
In general manner, aircraft that are piloted by two pilots have conventional flight control members that are mechanically coupled together and that individually or simultaneously serve to move a mechanical connection enabling the positioning of aerodynamic means to be modified relative to an incident air stream.
Nevertheless, there also exist electrical flight control members that are manually actuated by pilots and that also serve to generate control signals in the form of electrical signals representative of the positions of each of the control members.
Furthermore, with the appearance of electrical flight control members, it is no longer necessary to couple together two control members enabling each of the pilots to pilot the aircraft manually, either simultaneously or in alternation. In particular, such mechanical coupling is of no use for joysticks that are used specifically for controlling the aircraft in pitching and in roll, while making use of very small movements of the control member. Omitting such mechanical coupling is advantageous in that it enables the ergonomics of the cockpit of such a two-pilot type of aircraft to be improved.
Thus, and as described in particular in Document WO 2014/199212, it is known to use electrical flight control members (“fly-by-wire”) that are not mechanically coupled together. Nevertheless, under such circumstances, the dual operating mode in which each control member can control the aerodynamic means defaults to control logic of algebraically summing the control signals generated simultaneously by the two control members.
Thus, the resulting control setpoint could be zero, if the two control members are moved in opposite directions. Such a zero control setpoint then does not lead to any modification in the path of the aircraft, which can be dangerous when piloting certain aircraft that must respond rapidly to control signals. For example, with rotorcraft, it is necessary by default for one of the two pilots to be able to act quickly in order to correct a path. That pilot must thus have full control authority enabling the aerodynamic means to be moved over a full travel amplitude.
Furthermore, Document WO 2014/199212 does indeed describe an operating mode in which one of the control members can have priority over the second control member. Under such circumstances, a priority button enables priority to be given to only one of the two control setpoints issued by one of the two control members.
Nevertheless, under such circumstances, the logic of algebraically summing the control setpoints is conserved. Consequently, the control member that has priority over the second member does not have full authority over the aerodynamic means of the aircraft. In other words, even if such a priority button enables one of the two control members to be made inoperative, it does not enable the priority control member to control the aerodynamic means of the aircraft over a full travel amplitude.
Elsewhere, Documents EP 2 857 312 and U.S. Pat. No. 5,404,305 describe the general principle of a control system enabling an aircraft to be piloted by two pilots, each operating a respective control member.
Nevertheless, those two documents relate solely to a “training” mode corresponding to control logic involving summing of the control setpoints from the two control members, as described in Document WO 2014/199212.
Finally, control systems are also known, as described by Documents US 2012/053735 and EP 2 518 578, in which a single aircraft pilot can take control of the aerodynamic means of the aircraft when the autopilot of the aircraft is activated. Under such circumstances, the aerodynamic means of the aircraft can be piloted either by the autopilot or by two control members operated by two pilots with summing logic as described in Document WO 2014/199212.
Nevertheless, under such circumstances, the described methods and systems do not relate to two control members that are to be moved by respective people such as pilots of the aircraft, each having exclusive control over the control surfaces of an aircraft.